Browsing by Author "Hwang, LC"

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An exact analysis of an asymmetric polling system with mixed service discipline and general service order
(1997-12-01)
Hwang, LC
;
Chang, CJ
;
電信工程研究所
;
電信研究中心
;
Institute of Communications Engineering
This paper derives the exact mean waiting time fur an asymmetric polling system with general service order and mixed service discipline. The mixed sen ice discipline means that the service discipline of each stage (a turn in the service order sequence) for the same station can be gated or exhaustive. The general service order denotes that each station can be polled more than once in a polling cycle. We use the mean age and the mean excess of a cumulative time to obtain the mean waiting times fur stages and stations, where the cumulative time for a stage is defined as the total arrival time period of all customers that are served at one visit of the server to the stage. The accuracy of our analysis is verified by comparisons with previously published results and simulation results. We also use a genetic algorithm (GA) to search for an optimal pattern of service order and service discipline For the asymmetrical polling system. The results of the paper can be applied to the design of computer communication networks with polling schemes. (C) 1997 Elsevier Science B.V.
An exact analysis of an asymmetric polling system with mixed service discipline and general service order
(1997-12-01)
Hwang, LC
;
Chang, CJ
;
電信工程研究所
;
電信研究中心
;
Institute of Communications Engineering
This paper derives the exact mean waiting time fur an asymmetric polling system with general service order and mixed service discipline. The mixed sen ice discipline means that the service discipline of each stage (a turn in the service order sequence) for the same station can be gated or exhaustive. The general service order denotes that each station can be polled more than once in a polling cycle. We use the mean age and the mean excess of a cumulative time to obtain the mean waiting times fur stages and stations, where the cumulative time for a stage is defined as the total arrival time period of all customers that are served at one visit of the server to the stage. The accuracy of our analysis is verified by comparisons with previously published results and simulation results. We also use a genetic algorithm (GA) to search for an optimal pattern of service order and service discipline For the asymmetrical polling system. The results of the paper can be applied to the design of computer communication networks with polling schemes. (C) 1997 Elsevier Science B.V.
Analysis of a general limited scheduling mechanism for a distributed communication system
(1999-08-17)
Hwang, LC
;
Chang, CJ
;
電信工程研究所
;
電信研究中心
;
Institute of Communications Engineering
This paper studies an alternative scheduling mechanism of general limited service discipline for a distributed communication system, where the distributed system has a modular architecture and the module has tasks in the queue. We successfully analyze the system by way of imbedded Markov chains acid use a recursive method to derive the mean waiting time of task. The arrival processes for modules are assumed to be Poisson processes; the service time of a task in queues and the walking time between queues are assumed to be generally distributed. We also presents an optimal-pattern design of the general limited scheduling mechanism for the distributed communication system via a genetic algorithm. A distributed communication system, if designed with the general limited scheduling mechanism and its optimal pattern, can be flexible to meet the system requirements as much as possible. (C) 1999 Elsevier Science B.V. All rights reserved.
Analysis of a general service nonexhaustive polling system using a heuristic combination method and pseudoconservation law
(1996-05-01)
Chang, CJ
;
Hwang, LC
;
電信工程研究所
;
電信研究中心
;
Institute of Communications Engineering
This paper is devoted to the analysis of the mean waiting time for a polling system with general service order sequence and nonexhaustive service discipline. We obtain an expression for the mean waiting time in terms of a so-called residual cycle time and derive a pseudoconservation law (PCL) to help improve the accuracy of estimations of the mean waiting time. By multiplying the estimations of the residual cycle times for all stations by equal and unequal constants, we obtain two separate solutions for the mean waiting time. We furthermore propose a heuristic method that combines these separate mean waiting times into a final solution for the mean waiting time. Numerical examples show that our combination method generates accurate estimations for the mean waiting times in both cyclic and general cases over all traffic loads.
Analysis of a general service nonexhaustive polling system using a heuristic combination method and pseudoconservation law
(1996-05-01)
Chang, CJ
;
Hwang, LC
;
電信工程研究所
;
電信研究中心
;
Institute of Communications Engineering
This paper is devoted to the analysis of the mean waiting time for a polling system with general service order sequence and nonexhaustive service discipline. We obtain an expression for the mean waiting time in terms of a so-called residual cycle time and derive a pseudoconservation law (PCL) to help improve the accuracy of estimations of the mean waiting time. By multiplying the estimations of the residual cycle times for all stations by equal and unequal constants, we obtain two separate solutions for the mean waiting time. We furthermore propose a heuristic method that combines these separate mean waiting times into a final solution for the mean waiting time. Numerical examples show that our combination method generates accurate estimations for the mean waiting times in both cyclic and general cases over all traffic loads.
Ping-pong flow control for ATM ABR traffic
(2003-09-01)
Ku, CY
;
Hwang, LC
;
Wu, HT
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, we propose an improved technique for congestion control, named as ping-pong flow control (PPFC), for asynchronous transfer mode (ATM) available bit rate (ABR) traffic. This is a rate-based flow control scheme, in which the rate regulation is achieved by directly adjusting the transmission rate in the source end station. The proposed algorithm uses a bipolar feedback strategy, which employs positive and negative feedbacks to control the transmission rate for different switch states. These states are determined using the traditional threshold-based method. We also introduce state early detection (SED), which enables the PPFC to control traffic flows more precisely and accurately at critical moments. The simulation results show that the proposed algorithm provides a higher throughput and lower cell loss ratio when compared to the well-known backward explicit congestion notification (BECN). Furthermore, these results also show that PPFC is robust against feedback losses. (C) 2003 Elsevier Science B.V. All rights reserved.